Numerous problems are encountered when using a hand-held camera that incorporates sound receiving and recording means, such as a video camera or a photographic camera. If the microphone is mounted on the rear of the camera facing the user, the user must turn or otherwise manipulate the camera to adequately receive sounds from the scene being imaged. Similarly, it is difficult to capture interactive conversation between the camera user and the camera subject if the microphone is mounted on the front or rear of the camera. Also, microphones that are mounted onto cameras often protrude significantly from the camera and therefore make the camera bulkier and more cumbersome to use and transport. Such microphones also do little to reduce the detection of noise that is generated by the camera.
Numerous approaches have been used to reduce background noise and/or increase the directionality of microphones used for various purposes. For example, U.S. Pat. No. 4,436,966 by Botros is directed to a tele-conference microphone unit wherein a transducer is disposed between two dish-like sound collectors. The transducer is placed at the junction of two dish-like sound collectors which are back-to-back with their convex sides and an opening in each dish exposes the transducer to its concave side.
U.S. Pat. No. 4,742,548 by Sessler et al. discloses a unidirectional second order gradient microphone. Baffles are used to improve the directionality and frequency response of the microphone.
U.S. Pat. No. 4,009,355 by Poradowski discloses a reversible anti-noise microphone for use in a communications headset. The device uses a transducer to which there are two exclusive paths. The lengths of the paths are inherently unequal and unequal acoustical resistances are used in each path to equalize the response to sounds from the front and rear.
U.S. Pat. No. 5,226,076 by Baumhauer, Jr. et al. is directed to a directional microphone assembly. The assembly is constructed from a first order gradient (FOG) microphone element enclosed within a housing that is molded from an acoustically opaque material, such as Ethylene-Propylene-Diene-Monomer. Acoustic waveguides are used to increase the path distance between opposite sides of the transducer and improve sensitivity. The microphone is configured to be embedded within an exterior surface of sound-input equipment with both openings of the housing located along the exterior surface.
U.S. Pat. No. 5,282,245 by Anderson discloses a tubular bi-directional microphone used in a telephone. The microphone provides a bipolar response pattern and cancels unwanted noise incident upon the microphone at the sides of the tubular member, as well as noise above a particular frequency dictated by the length of the tubular member. The tubular members are preferably flared.
There remains a need for an inexpensive means for bi-directional sound detection with good noise cancelling characteristics, particularly for cameras and similar devices. It would be advantageous if the directionality was increased as compared to prior art devices and undesirable noise detection was reduced, including noise from the camera. Further, it would be advantageous if a substantial protrusion from the body of the camera was not necessary. This is particularly important due to the increased miniaturization of cameras designed to be handheld and easily transported.